1. Field of the Invention
The present invention relates to a phase-shift blankmask and a photomask, and more particularly to a phase-shift blankmask and a photomask which can achieve a fine pattern of not greater than 32 nm and preferably not greater than 14 nm.
2. Discussion of Related Art
Today, a finer pattern of a circuit has been continuously demanded in accordance with higher integration of large-scale integrated circuits (ICs). In case of a blankmask, a binary blankmask and a phase-shift blankmask have been conventionally developed and commercialized, and a binary blankmask having a hard film has recently been developed and used for a hard mask.
With recent achievement of a high-precise and fine pattern of not greater than 32 nm, a phase-shift blankmask with a hard film has been developed. The phase-shift blankmask with the hard film has a basic structure where a light-shielding film, the hard film and a resist film are stacked on the phase-shift film, and the hard film is made of a compound that generally contains silicon (Si) to secure etch selectivity against the under light-shielding film at dry etching.
However, the following problems arise since the hard film is made of the silicon (Si) compound. First, as the hard film made of the silicon (Si) compound contacts the bottom of the resist film, an electron charge-up phenomenon occurs in the hard film during an exposure process using an electron beam for manufacturing a photomask. The electron charge-up phenomenon causes a curved movement of electrons during the exposure process, thereby causing a position error while manufacturing the photomask. Therefore, it is difficult to apply the hard film made of the silicon (Si) compound to the exposure process based on double patterning, multi-patterning or the like technique where a pattern position is more strictly controlled.
Further, there is a problem of adhesion between the hard film made of the silicon (Si) compound and the resist film. In other words, high surface-energy of the hard film made of the silicon (Si) compound causes the resist film to be partially uncoated on the hard film when the resist film is applied or to be peeled off after a development process following the exposure process. To solve such a problem of adhesion between the resist film and the hard film, hexamethyldisilazane (HMDS) and the like surface treatment process has been performed. However, the additional surface treatment process such as the HMDS may cause a defect. For example, spot or scum defects may occur due to strong adhesion of the HMDS after the development process.
If the under light-shielding film is etched using the resist film as an etching mask after forming the light-shielding film on the phase-shift film without using the hard film, it is also difficult to form a fine pattern of not greater than 32 nm because of the thickness of the resist film, loading effects, etc.
By the way, research on the phase-shift blankmask has recently been conducted so that the phase-shift film can have high transmissivity without limiting the transmissivity to about 6%. The phase-shift blankmask having high transmissivity can get a fine the pattern by setting the transmissivity to about 6% or higher and increasing destructive interference at a pattern edge portion. However, the phase-shift film needs to have a thickness of not less than about 1000 Å in order to satisfy optical properties such as the transmissivity, a phase-shift degree, etc. and it is thus difficult to make a fine pattern since this thickness is greater by 1.5 times than a general thickness (650 Å˜700 Å) of the phase-shift film. Besides, if a lot of light elements are contained so as to increase the transmissivity of the phase-shift film, defects may occur while forming the pattern since the chemical resistance becomes weak.